package Internet;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;

public class UdpEchoServer {
    private DatagramSocket socket=null;
    public UdpEchoServer(int port) throws SocketException {
        socket=new DatagramSocket(port);
    }
    public void start() throws IOException {
        while(true){
            //1.读取请求并解析
            DatagramPacket requestPacket=new DatagramPacket(new byte[4096],4096);
            //输出型参数
            socket.receive(requestPacket);
            String request=new String(requestPacket.getData(),0,requestPacket.getLength());
            //2.根据请求，计算响应
            String response=process(request);
            //3.把响应返回给客户端
            DatagramPacket responsePacket=new DatagramPacket(response.getBytes(),response.getBytes().length,
                    requestPacket.getSocketAddress());
            socket.send(responsePacket);
            //4.打印日志
            System.out.printf("[%s:%d,request:%s response:%s]\n",requestPacket.getAddress().toString(),requestPacket.getPort(),request,response);
        }
    }

    //将private改为public，方便方面有新功能，可以进行重写
    public String process(String request) {
        return request;
    }
    public static void main(String[] args) throws IOException {
        UdpEchoServer udpEchoServer=new UdpEchoServer(1777);
        udpEchoServer.start();

    }
}
